[Basic steps of EEG topogram analysis development by the Livanov's school].

The basic steps of development of the topogram analysis technique are outlined with its prerequisites. A topogram is defined as a set of momentary EEG values simultaneously recorded from the whole scalp surface with multiple electrodes. Experimental evidence points to existence of two main types of the spatiotemporal organization of the cortical potentials varying in time in the whole range of the EEG frequencies. Animal and human experimental data are described which reveal either dominance of one of these types or their complex interaction.

Emotionality and the temporospatial organization of instantaneous EEG potentials.

The characteristics of the temporospatial organization of cerebral cortical potentials at different levels of genetically determined emotionality were analyzed by constructing topograms of instantaneous EEG levels in the inbred rat strains MR and MNRA. Two parameters were calculated for each topogram: the total level and the similarity coefficient. Power spectra were calculated for the values and these were found to change in an oscillatory manner. Interstrain differences were found in the correlated changes in total levels and similarity coefficients, in the durations of changes in the total level, which were more marked than those of similarity coefficients, and the nature of interhemisphere asymmetry. In MR rats, the power spectra of both measures showed significant peaks with modes at 2.0, 6.5, and 9.0 Hz. In MNRA rats, peaks in the spectra of these measures both coincided (2.0 Hz) and differed (7.0 Hz in the spectrum of the total level and 3.0, 4.5, and 6.0 Hz in the spectrum of the similarity coefficient). These data suggest different types of functioning of the reticulothalamocortical and hippocampocortical systems in rats of these strains.

[Emotionality and spatio-temporal organization of momentary EEG potentials].

With the aim to reveal features of the neocortical spatiotemporal organization of potentials characteristic of different genetically predetermined emotional levels, momentary values of EEG potentials were analyzed in inbred rats of MR and MNRA strains. A topogram was described by a basic parameter such as its general level (the mean of momentary values of potentials derived from 24 symmetrical electrodes bilaterally implanted into the brain cortex) and a similarity coefficient (correlation between the set of its momentary values and that of a standard topogram). The general level and similarity coefficient values were calculated for a series of successive topograms individually for the right and left hemisphere. Also, right- and left-side power spectra of these series were calculated. In rats of MR strain, significant (p < 0.05) peaks in the general level and similarity coefficient spectra were observed in the delta (2.0 Hz), teta (6.5 Hz) and alpha (9 Hz) frequency bands. In this strain, the general level power was higher at the right side, and the similarity coefficient power displayed the left-side dominance. In rats of MNRA strain, peaks in the delta(2.0 Hz) band coinsided in the general level and similarity coefficient spectra, whereas, independently, the general level spectra had peaks in the theta band (7.0 Hz), and similarity coefficient had peaks at frequencies 3.0, 4.5, and 6.0 Hz. The left-side general level spectral power was higher than the right-side general level spectral power in the delta and lower in the high-frequency theta bands. The similarity coefficient power displayed the left-side dominance for the peaks in the delta (2.0 Hz) and theta (3.0 Hz) bands, and it displayed the right-side dominance for the peaks in the theta (4.5 Hz) band. The specific features of the cortical spatiotemporal organization of potentials revealed in rats of MR and MNRA strains suggest different modes of functioning of at least two systems, reticulo-thalamo-corticaland hippocampo-cortical.

[System changes in the cortical electrical activity and their role in integrative processes in the brain (a synergic approach)]. / Sistemnye izmeneniia korkovoi élektricheskoi aktivnosti i rol' ikh v integrativnykh protsessakh golovnogo mozga (sinergeticheskii podkhod).

In the paper, the general theory of systems is applied to a description of the spatio-temporal organization of the summary cortical potentials, synergetic approach is applied for the insight into the functioning of their system changes. This made it possible to consider the human and animal cortical potentials recorded under different experimental conditions from the single viewpoint. The system organization of cortical potentials in multiple derivations was revealed by comparison of momentary topograms (a sequence of momentary values of cortical potentials in all recording points). This technique enables simultaneous estimation of the spatial and temporal characteristics. In the analyzed data array, the independent changes in different types of subsystems of spatial relations between the momentary potential values were found. These subsystems possess both the spatial and temporal characteristics. Parameters of such coexisting dynamic subsystems widely distributed over the cortex present information about the different indices of the system spatio-temporal organization of cortical potentials (STPO), however, only the ratio between the reflected processes is related with the functional features of cortical activity. The brain state and specificity of performance is to a greater extent determined by a reorganization of the topogram relief. The described relatively stable global system relations of cortical potentials during the organism adaptation to the environment principally change under conditions of goal-directed or voluntary activity. In parallel with the increasing role of developing short-term STPO variations, it was found that each stage of performance is characterized by the dominant topogram reliefs. Such reliefs probably present the "order parameters". They can determine spatial characteristics of the new self-organizing in transition periods dynamic systems of cortical potentials, which are related with the forming new functional states of the cortex. It was demonstrated that the functional possibilities of the brain cortex are determined both the dynamics of topogram reliefs and competing or cooperative interaction of the cortical STPO subsystems. The obtained evidence suggest that in parallel with the regional processes closer related with the projection areas of the brain cortex, a global spatio-temporal organization of cortical activity widely distributed over the cortex forms. The role of this organization of the cortical potentials in the integrative brain activity and expedient human and animal behavior is discussed on the basis of the authors' experimental and literature data.

Temporospatial organization of membrane-synaptic modifications and topograms of slow oscillations in cortical potentials during learning.

This report concerns the important question of the specificity of the organization of the different stages of formation of a conditioned reflex, considered at the level of membrane-synaptic modifications, which are compared with changes in the spatial organization of slow cortical potentials. A defined sequence of involvement of cellular mechanisms is demonstrated during learning, which may be responsible for various features of the spatial organization of slow cortical potentials. Changes in cellular excitability in cortical neurons are probably connected with oscillations in the overall level of instantaneous topograms and, thus, with the general level of spatial synchronization; the involvement of excitatory and inhibitory synaptic connections (with efficiencies corresponding to different stages in the reflex) may determine the formation of the relief seen in topograms. Parameters at both levels depend on the effects of the hypothalamus on the cortex.

[The subsystems of the spatial-temporal organization of cortical potentials and their role in EEG spatial synchronization]. / Podsistemy prostrantsvenno-vremennói organizatsii korkovykh potentsialov i ikh rol' v prostranstvennoi sinkhronizatsii EEG.

Studying successive topograms of potentials made it possible to reveal different types (subsystems) of the spatio-temporal organization of human and animal cortical electrical activity, which covered significant cortical surface. The dominance of the inversion of the sagittal potential gradient in the topograms of the resting state or complicated relief forms in the active states co-existed with oscillations of the mean level of topogram potentials, the contribution of which to the spatial EEG synchronization changed depending on the functional state of the brain. The role of the ratio between these subsystems was shown and the influence of this ratio was demonstrated on the spatial synchronization of cortical potentials in experiments with 11 rabbits (in the course of their adaptation to the environment and learning) and examination of 50 healthy adult subjects (during motor task performance and elaboration of verbal set). The spatial synchronization of cortical potentials was found to have a complex structure, which was determined by the ratio between the effects of subsystems of the spatio-temporal organization of cortical potentials.

[The spatial-temporal organization of the cortical potentials in freely moving rabbits during active behavior arising under the influence of intrinsic needs]. / Prostranstvenno-vremennáia organizatsiia korkovykh potentsialov svobodnopodvizhnykh krolikov pri aktivnom povedenii, voznikaiushchem pod vliianiem vnutrennikh potrebnostei.

The studies of successive momentary topograms of cortical potentials in freely moving rabbits revealed peculiarities of the regulation of the EEG spatial synchronization (SS) during rest and active phases of the basic behavioural cycle. The animal's movements of the active phase caused by intrinsic need were related to an increase in the influence of the global level fluctuations of the momentary topograms. During conditioned motor activity the topogram relief reorganization played a prominent part in the process of the SS formation. Comparison of these data allowed a conclusion that the peculiarities of the SS structure of the cortical potentials were determined by the ratio between the two processes which make up the EEG spatio-temporal organization rather than the degree of their expression. In case of the dominance of the topogram relief reorganization the state of the animal was related with the most frequently occurring topogram forms.

[The spatial-temporal organization of the membrane-synaptic modifications and of the topograms of the slow fluctuations in the cortical potentials during learning]. / Prostranstvenno-vremennáia organizatsiia membranno-sinapticheskikh modifikatsii i topogramm medlennykh kolebanii korkovykh potentsialov pri obuchenii.

This paper deals with an actual problem of specificity of organization of different stages of a conditioned reflex (CR). We suggest to consider this problem at the level of membrane-synaptic modifications comparing them with the indices of changes in the spatial organization of slow potentials in the cortex. The definite sequence of involvement of cellular mechanisms has been shown which can determine different features of the spatial organization of cortical slow potentials. Changes in cellular excitability of cortical neurons are probably connected with the variations of the general level of momentary electroencephalotopograms and, correspondingly, with the level of general spatial synchronization. Involvement of excitatory and inhibitory synaptic connections (with the efficiency corresponding to CR stages) determines the formation of electroencephalotopogram relief. Indices of both levels depend of hypothalamic effects on the cortex.

[The characteristics of the spatial-temporal organization of the cortical potentials in the free-moving rabbit during training (a comparison of the stages in the generalization and specialization of the conditioned-reflex response)]. / Osobennosti prostranstvenno-vremennói organizatsii korkovykh potentsialov svobodnopodvizhnogo krolika pri ego obuchenii (sravnenie stadii generalizatsii i spetsializatsii uslovnoreflektornogo otveta).

Analysis of successive topograms was applied to investigation of peculiarities of the spatio-temporal organization of cortical potentials of a rabbit at different stages of conditioning. Qualitative distinctions were shown between the stages in the character of regulation of the spatial synchronization (SS) related to variations in cortico-subcortical relations. Higher SS level at the stage of generalization changed for more complicated pattern of the spatio-temporal organization of cortical potentials. These complex spatio-temporal characteristics favoured facilitation of excitation spreading along the paths which provide specialization of the conditioned response under the action of the conditioned stimulus. Obtained results were correlated to specific membrane and synaptic modifications in the course of conditioning. The findings extend the notions of the cellular mechanisms which determine the features of the cortical SS at the stages of generalization and specialization of the conditioned reflex.

[The functional testing of the interhemispheric asymmetry in the spatial organization of rabbit cortical potentials]. / Funktsional'noe testirovanie mezhpolusharnoi asimmetrii prostranstvennoi organizatsii korkovykh potentsialov krolika.

Interhemispheric asymmetry was studied of spatial-temporal potentials organization (STPO) of the cortex in non-fixated animals in the states of deep rest, behavioural activity and in the transition period between them. Despite the intrahemispheric differences of the STPO in each of these states, interhemispheric divergences in the character of reconstructions of momentary topograms of the cortical potentials, recorded at 24-channels leading, are limited by 35% of the epoch analysis time. Comparison of the dynamics of intrahemispheric changes of topograms of cortical potentials in the left and right hemispheres in the states of rest and activity revealed a narrowing of temporal period of the absence of resemblance in reconstructions of successive topograms of the left and right hemispheres in comparison with transition processes. In the phase of rest the interhemispheric conjugation of spatial reconstructions in topograms became lowered mainly because of the disturbances of monotony of changes of their reliefs in one of the hemispheres in turn. In the active phase, deviations from STPO of the cortex, characteristic of the state of rest, were met more frequently in the right hemisphere; in that case oscillations of the topograms general mean level connected with the activity of non-specific activating subcortical brain system acquired a significant role in regulation of interhemispheric relations. Presence of interhemispheric resemblance of reconstructions of topograms reliefs in the active phase, despite the tendency to its lowering in comparison with the rest, testifies to the contribution also of the intracortical processes to the interhemispheric spatial synchronization of the cortical potentials in this state.

[The spatial organization of the cortical potentials in exposure to different forms of photic stimuli]. / Prostranstvennaia organizatsiia korkovykh potentsialov pri vozdeistvii svetovykh razdrazhitelei razlichnoi formy.

Reactive changes of spatial-temporal organization of cerebral cortex potentials of rabbits under the action of light stimuli of various shapes (circle, square, triangle, cross and weaker diffusive light presented prior to and after the application of structural stimuli) were studied on the basis of multi-channel EEG recording data (24 leads). The data were evaluated of spectral-correlative analysis of the electrical activity and the results of comparison of successive momentary topograms of cortical potentials (EEG) on two-second segments prior to and during the action of the applied light stimulus. The obtained results showed that localization of interconnected changes of the cortical potentials were more sensitive to the perception of the form of light stimuli than the change of frequency characteristics of the EEG rhythms.

[The interhemispheric asymmetry of the spatial-temporal organization of cortical potentials in the rabbit]. / Mezhpolusharnaia asimmetriia prostranstvenno-vremennói organizatsii korkovykh potentsialov krolika.

In experiments on freely moving rabbits the existence of interhemispheric asymmetry of spatial-temporal organization of the cortical potentials in the state of calm alertness was shown. Episodes were revealed of interhemispheric discordance of spatial reconstructions of momentary reliefs of the cortical potentials topograms 1/64-1/3-1/5 s in duration, i.e. periods of the theta- or delta-rhythms. Total duration of time of interhemispheric asymmetry (according to significant divergences in dynamics of resemblance coefficients of consequent reliefs of the cortical potentials topograms) in most cases was not less than 10% and not more than 30% of time of analysis epoch and consisted of discordance episodes both of different global reconstructions of spatial correlations of the left and right hemisphere potentials and of interhemispheric local shifts in spatial organization of the cortex potentials.

[Quantitative assessment of maps of the cortical background potentials during the adaptation of freely moving animals to environmental situations]. / Kolichestvennaia otsenka kart fonovykh potentsialov kory pri adaptatsii svobodnopodvizhnykh zhivotnykh k okruzhaiushchei obstanovke.

Utilization of spectral-correlation methods of EEG analysis, due to necessary averaging in time, does not make it possible to detect dynamic phenomena in spatial-temporal organization of brain potentials. Non-traditional method is presented of quantitative evaluation of the changes of spatial-temporal correlation of cortical potentials--comparison of successive momentary potentials relief (electroencephalotopograms--EETG). Joint utilization of dynamics of similarity coefficients of successive EETG (Ket), mean values of EETG (Yet) and some other parameters allows to judge about dynamic properties of spatial correlations of potentials of freely moving animals in adaptation process to the environment during which alternation is established of the active and passive phases in decaminute intervals. Quantitative evaluation of spatial-temporal organization of the parameters of rabbits cortical potentials in these phases and in transition periods has revealed their informative possibilities.